Novel green and more efficient reaction for the synthesis of aromatic hydrazides

Abstract

Development of new lanthanide-based sensors depends on the rational design of ligands containing multiple coordination sites and planar π-delocalized systems for light reception.[1] In this work we present a novel, one-step reaction for the synthesis of aromatic hydrazides, precursors in the synthesis of the final organic ligands designed for the coordination with the lanthanide ions. The synthetic strategy implicates the reaction between a naphtoic carboxylic acid (among others) and hydrazine monohydrate, using 1,1'- carbonyldiimidazole (CDI) as coupling agent and THF as solvent.[2] We also add 4-dimethylaminopyridine (DMAP) and N,N’-diisopropylethylamine (DIPEA) as bases (Figure 1). The reaction is completed at room temperature overnight. This is a non-reported alternative to the classical two-step approach, which includes the preparation of the desired hydrazide from its corresponding carboxylic acid; which is first esterificated and subsequently treated with hydrazine monohydrate, taking up to 24 hours of reflux conditions for each reaction.[3]